In order to record under optimal recording conditions, optical discs having recording functions are provided with test recording areas. When an optical disc has a plurality of recording layers and the layer being recorded on is a lower layer, as viewed from the side on which the recording light is incident, the optimal conditions differ depending on whether the layer or layers above are in a recorded state or not, so it is necessary to know the state of the upper layer or layers.
A known strategy is to check the recording state of the layer(s) above the layer onto which information will be recorded and make a test recording under the same conditions (refer to Patent Document 1, for example).    Patent Document 1: Japanese Patent Application Publication No. 2000-311346 (pp. 1 to 15, FIGS. 1 to 8)